well... when I started this game I was in a similar situation. Based on a small airport with not much room for growth with only one a/c type. So I decided to go for a mix of second-hand DC9-30 and F27, until the airport became too small for them too. But, by then I had enough muscle to open a second base. I have now grown into a 90+ a/c airline, valued over two billions. My fleet today consists of MD81/82/83/87, ATR42/72 (all owned, almost all bought brand new) and 8 leased Tri Star 500:s.
So, I would say, go for it!